Conventionally, a vehicle seat sliding device that includes a lower rail that is fixed to a floor of a vehicle and extending in the vehicle front-and-rear direction, and an upper rail that is fixed to a vehicle seat and is assembled to be slidable to the lower rail has been known (Japanese Laid-open Patent Publication No. 2007-055557). In Japanese Laid-open Patent Publication No. 2007-055557, a screw member including a male screw that meshes with a female screw of a nut member fixed to the lower rail is provided on the upper rail, and as the screw member rotates, the upper rail slides with respect to the lower rail. The distal end portion of the screw member is rotatively inserted to a through hole of a supporting member fixed to the upper rail and provided with the through hole and is supported suppressing the vibration of the screw member due to the rotation.
However, there has been a problem in that, when the screw member is curved along the axial direction, the crossing angle of the central axis of the distal end portion of the screw member and the central axis of the through hole of the supporting member gets larger, and the screw member gets difficult to rotate smoothly as the screw member bites into the supporting member, thereby making it difficult to slide the seat smoothly with respect to the floor.
Thus, one of the problems of the present invention is, for example, to obtain a vehicle seat sliding device of a novel configuration that is capable of sliding the seat more smoothly with respect to the floor as the screw member rotates smoothly.